comparison of tetric n-bond micro-tensile bond strength with qth and led light-curing units

the objective of this study was to examine the effects of two types of light-curing units, namely, qth and led on the micro-tensile strength (mtbs) of tetric n-bond (combined primer and bonding agent). a total of 20 extracted sound human first premolars were separated into two groups, each of which comprising ten specimens. the surface enamel of specimens for each group was removed by means of a cylindrical diamond bur (tizkavan, iran) until dentin was exposed. next, gelatin capsules, composed of tetric n-ceram composite paste, were vertically bonded to the dentin in samples of both groups by means of a light-cure adhesive; however, the curing process in group 1 was performed using led and in group 2 by a qth device. crowns of all specimens were divided into vertical slabs of approximately 1 mm thickness in an occluso-gingival way. slabs were prepared into hourglass shapes with a width and thickness of 1 mm and 0.8 mm in each group. micro-tensile bond strength was discovered utilizing a testing machine (instron-universal testing machine- germany.) it was found that led-cured specimens had a higher micro-tensile bond strength with a significant difference from the qth-cured ones (p 0.05). the light devices have an impact on the micro tensile bond strength of resin adhesives.